Method and device for centering irregularly formed, substantially cylindrical workpieces, such as logs



May 29, 1962 P. v. RAURA 3,036,607

METHOD AND DEVICE FOR CENTERING IRREGULARLY FORMED, SUBSTANTIALLYCYLINDRICAL WORKPIECES, SUCH AS LOGS Filed June 25. 1959 INVENTOR:

PENTTI VALD R RAURA Attorney United States Patent 3,036,607 METHOD ANDDEVICE FOR CENTERING IRREG- ULARLY FORMED, SUBSTANTIALLY CYLIN- DRICALWORKPIECES, SUCH AS LOGS Pentti Valdemar Raura, Kristinehamn, Sweden,assrgnor to Aktiebolaget Furuplywood, Kristinehamn, Sweden, a Swedishjoint-stock company Filed June 25, 1959, Ser. No. 822,959 Claimspriority, application Sweden July 1, 1958 2 Claims. (Cl. 144-209) Thisinvention relates to a method and a device for centering irregularlyformed workpieces, such as logs, which are to be treated, e.g. turned,around a predetermined center line.

When veneer is to be turned from wood logs, a center line for the logis, as a rule, determined by the eye in connection with fixing theworkpiece in the lathe with help of mechanical lifting appliances ormanually. Certain simple hand tools are also used for finding thiscenter line. However, in some cases, for certain kinds of wood, a centerline is used which is displaced in relation to the geometrical centerline of the log, substantially with a view to obtaining certainwood-technical effects.

The logs which are cut from a trunk, obtain a form which very nearly canbe described as a truncated cone, which complicates the centering. Whenthe trunk, as often occurs, is crooked also the log will, to a certainextent, suffer from this drawback. Furthermore, there may also be otherformal defects, viz. root folds and great surface and bark damages. Asalready mentioned, one has, by the eye, tried to pay regard to theseerrors when fixing the log in a veneer lathe. The intention is to obtainthe greatest possible yield from the log, i.e. to obtain a log ofcylindrical form when turning and with the least possible waste ofmaterial, and thus the greatest possible quantity of whole, singleveneer.

The device described below is designed in such a mannor that at the sametime as it lifts the log into the veneer lathe, it automaticallydetermines the desired center line and corrects the errors usuallyoccurring in logs, such as crookedness, conicity and great surfacedefects.

The invention is substantially characterized in that the center isdetermined in two cross sections located at a certain distance from theends of the workpiece, starting from three points on the periphery ofeach cross section, raising the workpiece while it is supported at twopoints so that the center of each cross section follows a definite lineand, when the center has reached a definite position, stopping theworkpiece by means of an impulse supplied by a feeling member when saidfeeling member which is displaced in dependence upon the liftingmovement and in the opposite direction, travels towards the workpieceand forms the third point on the periphery of the cross section.

Furthermore, the invention relates to a device for finding the center,which is characterized by two independent lifting devices, eachsupporting the workpiece at a definite distance from the ends of theworkpiece, and each comprising a feeling member adapted to be actuatedby the workpiece and guided by the respective lifting device, saidfeeling member stopping the movement of the lifting device when theworkpiece has reached the desired position. Each lifting device may beprovided with a lifting member which is designed as an arm on which theworkpieces rest, and thus serves as a magazine. That part of the liftingmember which supports the workpiece, is so designed that the circlecenter determined by the supporting points and the third point islocated in a definite position. If there are errors in the workpiecewhich the device does not pay regard to, the centering is cor- 3,036,607Patented May 29, 1962 rected by raising or lowering the common centerpoint of the lifting and feeling members. When the feeling member hasreached its highest position, it is turned for removal of the core andfor replacing of the lathe tool. A feed device located on the arm feedsa workpiece one at a time.

An embodiment of the invention will be hereinafter described, referencebeing bad to the accompanying drawing, in which- FIG. 1 is a lateralelevation of the device,

FIG. 2 an end view,

FIG. 3 a plan view, and

FIG. 4 a feed device.

The workpiece 1 is placed on two spaced arms 2 whereafter it slides, byits own weight, along the arms towards a feed device comprising a part 3which is so designed that it feeds a workpiece when it is actuated by aforce P through a bar 5. A force F is, through bars 6, transmitted tothe arms 2 so that the latter raise the workpiece and the movement ofthe arms is transmitted by link arms 7, 8 and 9 to a bar 11 guided byrollers 10. On said bar 11 there is fixed a feeling member 12 providedwith a cross piece 13 which is tangential to the periphery of theworkpiece. The impulse supplying part or cross piece 13 of the feelingmember 12 acts as a contact element which is operatively connected tothe means for moving arms 2 and is arranged to stop the lifting movementof the said arms at contact with the workpiece 1. With regard to qualitydefects the centering may be controlled by raising or lowering thelifting and feeling members. This takes place by means of a bar 14 whichactuates a bellcrank lever 15 in such a manner that the link arm 8mounted thereon can be displaced in the vertical direction.

Fundamentally, the device determines the center points in two crosssections of the log if the cross section is circular. In reality thecross sections are slightly elliptical or irregular, but in practicethis is of no importance because the device determines the center,starting from three different tangent lines to the periphery of thecross section. When the shape of the log is a straight truncated cone,its center line is obtained by determining the center points in twocross sections taken arbitrarily on the log. If the shape of the log isa curved truncated cone, its center line is found with sufficientexactness by determining the center points in two cross sections locatedat a fourth of the total length of the workpiece from each end.

The lifting movement is obtained either hydraulically, pneumatically orelectrically or in some other suitable manner or by these methods incombination.

The device is preferably remote-controlled so that the machine operatorstarts the lifting movement while the centering itself and the returnmovement of the device take place automatically.

What I claim is:

1. A device for centering workpieces having a substantially cylindrical,but irregular, cross section in a lathe, comprising two independentlifting devices, each of said lifting devices comprising an arm which ispivotally supported at one end and which, at the other end, is shapedsuch that it will support a substantially cylindrical workpiece at twopoints on the periphery of the workpiece and at a definite distance fromthe ends of the workpiece, said pivotally mounted arms being adapted tosupport additional workpieces and thus serve as a magazine for feedingworkpieces to the lathe, and each lifting device also comprising afeeling member, lever means connecting each of said feeling members tothe respective lifting device, the construction and arrangement beingsuch that each feeling member is displaced 3 downward when the liftingdevice lifts the workpiece through an arcuate path, and is so actuatedby said workpiece that, when the feeling member contacts the workpiece,it supplies an impulse which stops the lifting movement when theworkpiece is centered in the lathe.

2. A device as claimed in claim 1, characterized by a feed devicearranged on the arm for feeding a workpiece one at a time.

References Cited in the file of this patent

